Update on Prospects for Drell Yan at RHIC

1. RHIC pC Polarimeters Absolute Polarimeter (H jet) Siberian Snakes Siberian Snakes PHENIX STAR Spin Rotators (longitudinal polarization) Spin Rotators (longitudinal polarization) Pol. H- Source LINAC BOOSTER Helical Partial Siberian Snake AGS 200 MeV Polarimeter AGS pC Polarimeter Strong AGS Snake Update on Prospects for Drell Yan at RHIC L.C. Bland Brookhaven National Laboratory Transverse Partonic Structure Workshop Yerevan, 26 June 2009

2. Outline • Motivation for transverse spin Drell Yan • Requirements • Progress towards large-y DY

3. Transverse Spin Drell Yan at RHIC vsπ-SiversAsymmetry in Semi-Inclusive Deep Inelastic Scattering • Important test at RHIC of recent fundamental QCD predictions for the Sivers effect, demonstrating… attractive vs repulsive color charge forces • Possible access to quark orbital angular momentum • requires very high luminosity (RHIC II) • both STAR and PHENIX can make important, exciting, measurements • o Transverse-Spin Drell-Yan Physics at RHIC L. Bland, S.J. Brodsky, G. Bunce, M. Liu, M. Grosse-Perdekamp, A. Ogawa, W. Vogelsang, F. Yuan http://spin.riken.bnl.gov/rsc/write-up/dy_final.pdf

4. Attractive vs Repulsive Sivers Effects Unique Prediction of Gauge Theory ! Simple QED example: Drell-Yan: repulsive DIS: attractive Same inQCD: As a result:

5. Experiment SIDIS vs Drell Yan: Sivers|DIS= − Sivers|DY *** Probes QCD attraction and QCD repulsion *** HERMES Sivers Results RHIC II Drell Yan Projections 0 Sivers Amplitude M. Diefenthaler arXiv:0706.2242 (final results from HERMES just released arXiv:0906.3918) 0 0.1 0.2 0.3 x

6. Rapidity and Collision EnergyTransverse Spin Asymmetries for the DY Processhttp://spin.riken.bnl.gov/rsc/write-up/dy-final.pdf Light mass DY, Mg*> 4 GeV/c2 Rapidity distributions for different s Large rapidity acceptance required to probe valence quark Sivers function, also where p+pp+X transverse spin asymmetries are found to be large at RHIC.

7. Benchmarking Simulations p+p  J/+X  l+l-+X, s=200 GeV PHENIX, PRL 98(2007) 232002 m+m- 1.2<|h|<2.2 e+e- |h|<0.35 J/ is a critical benchmark that must be understood before Drell-Yan

8. cc bb Dilepton Backgrounds Drell-Yan J/  ’ Isolation needed to discriminate open heavy flavor from DY, and is possible at PHENIX with planned upgrades.

9. Summary of Transverse SSA Drell-Yan Requirements • 250 pb-1 transverse polarization Drell-Yan data sample probes Sivers function sign relative to SIDIS. • Isolation required to discriminate low-mass DY from open-heavy flavor. • Large rapidity will require tracking for charge-sign discrimination. • Likely optimal at s = 500 GeV, given demonstrated luminosity • Useful to pursue DY measurement where |AN|>0 is found for p+pp+X • Large rapidity will require benchmarked simulations to establish tracking requirements. Benchmarking starts with J/ (see below).

10. LuminosityRun-9 performance Source: RHIC Collider Projections, W. Fischer et al. (2009) • Challenges remain to be overcome to realize the best-case scenarios • Luminosity increases at s=500 GeV relative to s=200 GeV were realized • Depolarizing resonances in RHIC will require new tunes to reduce their impact

11. LuminosityFuture Projections Source: RHIC Collider Projections, W. Fischer et al. (2009) • Luminosity projections for s = 500 GeV are sufficient for transverse-spin DY • Improved polarization would be useful to achieve sufficient accuracy

12. STAR Detector Forward Meson Spectrometer commissioned/operated in RHIC run 8. Cluster-pair triggered readout of Forward Time Projection Chamber in ongoing RHIC run 9.

13. From FPD To FMS • 1264 Lead Glass Detectors • Full azimuthal coverage for 2.5 < η < 4 FPD Prior to Run 8 FMS Run 8 and beyond

14. C.Perkins, QM09 FMS Detector • 20x more acceptance than previous forward electromagnetic calorimeters at STAR Geometric Efficiency: J/Psi xF FPD FMS • Increased acceptance not only increases pion yields and kinematic range but also give much higher geometric efficiency for high-xF J/Psi

15. Field Effects • Does the signal survive the field? • Radial and Azimuthal fields impart impulses in the Φ direction • These impulses are small and in opposite directions (they nearly cancel each other) • Field effects on our signal are small C.Perkins, DNP08

16. FMS Minbias Simulations and Association Analysis • Fast J/ψ generator + full GEANT simulations • Simulation : • PYTHIA 6.222 + full GEANT simulations • 9.2 nb-1 Integrated Luminosity • Data : • Plot includes < 1% of full data set • Reconstructed quantities match generated quantities quite well • Full simulation models Mpair data very well C.Perkins, QM09

17. Forward p+p J/ψ – 2-Cluster Analysis Reconstructed 2-cluster invariant mass Fit with Gaussian + Polynomial Gaussian Fit Parameters: • μ = 3.083 ± 0.017 GeV/c2 • σ = 0.028 ± 0.011 GeV/c2 • χ2/d.o.f. = 24.6/25 • Significance from fit • 2.1 σ Background Simulation: • Needs more statistics • Normalized to integral of data • Cuts Applied: • Epair > 60.0 GeV • energy sharing, Zpair < 0.7 • Isolation Radius: • 0.5 Dh-Df C.Perkins, QM09 • pair mass background modeled well by simulation • significance of J/ not large here, but including requirements on pT,cluster further reduces background by suppressing low-pTp0 production.

18. Forward p+p J/ψ – 2-Cluster Analysis Reconstructed 2-cluster invariant mass / (~ 6 pb-1 Sampled Luminosity) C.Perkins, QM09 • Fit with Gaussian + Offset • Gaussian Fit Parameters: • μ = 3.080 ± 0.020 GeV/c2 • σ = 0.082 ± 0.026 GeV/c2 • χ2/d.o.f. = 20.83/26 • Significance from fit • 4.5 σ • Cuts Applied: • E_pair > 60.0 GeV • Zγγ < 0.7 • Isolation Radius: • 0.4 Dh-Df • pT_cluster > 1.0 GeV/c • high-xF J/ may have implications for intrinsic charm at large Bjorken-x in proton • use to benchmark simulations for future transverse-spin Drell-Yan experiment

19. Forward p+p J/ψ – 3-Cluster Analysis • Reconstructed invariant mass of candidate χC → J/ψ + γ events • Peak Counts = 8.40 ± 2.88 • 2.9 σ Significance • μ = 2.97 ± 0.025 GeV • σ = 0.070 ± 0.025 GeV • χ2/d.o.f. = 0.7 with 14 points fit. • Significance depends on background model • 2.9 σ significance with currently estimated background. C.Perkins, QM09

20. Why does high-xF intrinsic heavy flavor matter? • Diffractive Higgs production at the LHC via QQ in proton • May provide a clear signal for Higgs production due to small background • How can high-xF intrinsic heavy flavor happen? • Not from Gluon Splitting (extrinsic heavy flavor) • Heavy quarks are expected to be multi-connected to the valence quarks within a proton and appear at large x via… Phys.Rev. D73 (2006) 113005 QED QCD • Can intrinsic heavy flavor expectations be tested experimentally?

21. Status/Plan of Large-xF DY • Large-xF J/ production has been observed from bare large-y calorimeter response in RHIC run 8. • Cluster-pair trigger is operational for acquiring large-y tracking data in RHIC run-9. Pending analysis, requirements for future DY can be established (e.g., fast-tracking inside solenoid, space points in front of FMS). • Sufficient luminosity for p+p s=500 GeV collisions has been established; further development of polarization is required, as is measurement of AN(xF) for p+pp0+X at s=500 GeV and measurement of large-xF J/ and U production at s=500 GeV, to bracket light-mass DY region. • Technical solutions exist for fast tracking inside solenoid (GEM trackers) and space points in front of FMS (forward meson preshower). Construction to span 2.5<h<4 region is required, and could be completed in ~2 years, pending approval. • RHIC schedule is oversubscribed  DY would be after RHIC run 11 (>2011). • Run-10 will be Au+Au energy scan for deconfinement critical point search, and Au+Au at sNN=200 GeV. • Run-11 is expected to be polarized p+p, with unknown mix of s=200,500 GeV and longitudinal/transverse polarization.

22. Backup

23. BBC ZDC ZDC PHENIX Detector EMCal p0/g/h detection • Electromagnetic Calorimeter (PbSc/PbGl): • High pT photon trigger to collect p0's, h’s, g’s • Acceptance: |h|<0.35, f = 2 x p/2 • High granularity (~10*10mrad2) p+/ p- • Drift Chamber (DC) for Charged Tracks • Ring Imaging Cherenkov Detector (RICH) • High pT charged pions (pT>4.7 GeV). Relative Luminosity • Beam Beam Counter (BBC) • Acceptance: 3.0< h<3.9 • Zero Degree Calorimeter (ZDC) • Acceptance: ±2 mrad Local Polarimetry • ZDC • Shower Maximum Detector (SMD)

24. C.Perkins, QM09 Energy Dependent Corrections • Reconstructed photon energies were individually corrected as dictated by detector simulations. • Electromagnetic shower shape profiles and analysis code have been successfully adapted from FPD for use with FMS • When the p0(h) mass is properly reconstructed, so is its energy